Transparent resins have been widely used as the materials for molded products requiring transparency, such as automobile components, illumination equipments, and electric components. Recently, in addition to these application, other applications of these resins as optical materials or materials for electric components continue to progress.
The optical materials or materials for electric components require, in addition to transparency, a higher level of function that could not be satisfied by conventional common transparent resins, for example, a polycarbonate resin, a polymethylmethacrylate resin, and the like. For example, a base material for an optical disk as an optical material requires heat resistance, low birefringence, moldability, mechanical strength, adhesiveness to a recording layer, and the like.
As other resin materials in addition to the transparent resin, a hydrogenated product of a thermoplastic ring-opening metathesis polymer is excellent in transparency, heat resistance, low birefringence, moldability, or the like. Due to such characteristics, a hydrogenated product of a thermoplastic ring-opening metathesis polymer has been evaluated as a very suitable resin material that is excellent in physical strength, heat resistance, transparency, and low birefringence, as for the materials for plastic lens, a retardation film, or a polarizer protective film among the optical applications.
Patent Document 1 discloses a hydrogenated product of a ring-opening metathesis polymer, which contains a specific ratio of oligomers, such that it has high light transmittance and low birefringence, and as a result, it is very useful as a lens material. However, this document has no description of regulation of its refractive index that is an important factor for a lens.
In addition, Patent Document 2 discloses a polarizing film for a liquid crystal display, in which a thermoplastic saturated norbornene-based resin sheet is laminated as a protective layer on a polarizing film. The polarizing film is laminated on a liquid crystal substrate or a retardation film by a transparent acrylic adhesive, or the like, but it has a problem that it is difficult to exhibit adhesion strength.
The reason why sufficient adhesiveness cannot be obtained is that adhesion between a high-polarity polyvinyl alcohol and a low-polarity norbornene-based resin is effected.
Patent Document 3 reviews a method involving blending an oligomer of a norbornene-based resin having an enhanced polarity, which is obtained by polymerizing monomers containing an ester or an alcohol, with another norbornene-based resin to increase the adhesiveness and to lower the melt viscosity of the resin, thereby improving the moldability. However, the adhesion power by blending with a norbornene-based resin having an increased polarity is 0.07 kN/m, which is higher than 0.04 kN/m of the polarity when not blended therewith, but an effect of increasing the adhesion power is not sufficient. Also, the addition of the oligomer lowers the glass transition temperature, which in turn leads to a problem that heat resistance is lowered.
As for a method for further improving the polarity of a polymer, Patent Documents 4 and 5 each propose a method involving introducing a high-polarity carboxyl group. For introduction of a carboxyl group, a method in which cyclic olefins each containing an ester or an acid anhydride are copolymerized and then the ester or the acid anhydride is decomposed to obtain a carboxyl group, is disclosed, and further, Patent Document 6 discloses a method for directly copolymerizing cyclic olefins each containing a carboxyl group.
However, these documents mention a polymer containing a carboxyl group, but none of them disclose the relationship with heat resistance, melting characteristics upon melt molding, and optical properties and adhesiveness of the polymer containing a carboxyl group.
In addition, in the case where a polycarbonate, a polymethacrylate, a polystyrene, a cyclic olefin polymer, and the like, each of which has common transparency, are combined, and then applied as an optical material, small difference in the refractive indice is important since it does not cause light scattering such as refraction and reflection, and it is also necessary to arbitrarily control the refractive index by a polymer structure.
Moreover, if a hydrogenated product of a ring-opening metathesis polymer is used as an optical film or a molded product, a method for obtaining a film by a melt molding method, or a method for obtaining a molded product by injection molding had a drawback that the polymer gets deteriorated since high heat resistance leads to a molding temperature as high as 250° C. or higher, or that its appearance has defects due to generation of decomposed products, gels, or the like. Thus, there has been a need of development of a hydrogenated product of a thermoplastic ring-opening metathesis polymer, which has a high glass transition temperature, excellent heat resistance at a temperature used, and suitable flowability at a temperature zone for a molding process such as melt molding, or the like.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. H5-97978    [Patent Document 2] Japanese Unexamined Patent Application Publication No. H 6-51117    [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2003-3048    [Patent Document 4] Japanese Unexamined Patent Application Publication No. 2001-139776    [Patent Document 5] Japanese Unexamined Patent Application Publication No. H11-130843    [Patent Document 6] Japanese Unexamined Patent Application Publication No. 2004-2795